1. Field of the Invention
The present invention relates to polymerizable compositions, and more particularly to polymerizable compositions with excellent storage stability containing an aromatic sulfinate as a polymerization initiator.
2. Description of the Background
There is known as a means for polymerizing radical-polymerizable monomers the use of a sulfinic acid or a salt thereof, such as sulfinic acids, sulfinic acid or a salt-oxidizer system thereof, and sulfinic acid or a salt-amine-peroxide system thereof, as a component of a polymerization initiator. For example Japanese Patent Application Laid-open No. 30193/1978 discloses a process entailing the use of a sulfinate-amine-peroxide system as a polymerization initiator for radical-polymerizable monomers. Further Japanese Patent Application Laid-open No. 75907/1982 discloses that this sulfinate-amine-peroxide system is particularly useful for the polymerization of dental adhesives comprising an acidic monomer.
However, since aromatic sulfinates which have hitherto been used, e.g. benzenesulfinate and toluenesulfinate, gradually react with the double bond of the monomers such as (meth)acrylate, (meth)acrylamide or (meth)acrylamide derivative, compositions comprising the sulfinate dissolved or suspended in the monomer will lose the polymerization activity in a few weeks when stored at room temperature.
Thus, the two components must be stored in separate packages so that they wily not be in contact with each other. However, this is very disadvantageous compared to other systems which can be packed and stored together with both monomer and initiator.
Therefore, a need continues to exist for a composition containing a polymerizable monomer and a sulfinate, which composition has an extended storage stability.